Paramedics and other medical workers began to evacuate patients from New York University Langone Medical Center due to a power outage caused by Tropical Storm Sandy, followed by a failure of backup generators at the hospital, New York City officials said Monday night.

About 200 patients, roughly 45 of whom are critical care patients, were moved out of NYU via private ambulance with the assistance of the New York Fire Department, city officials said. ABC News' Chris Murphey reported a long line of ambulances outside of NYU Langone waiting to transport patients to other hospitals in the city.

The hospital had a total of 800 patients two days ago, some patients were discharged before tonight's evacuation, which was described by emergency management officials as "a total evacuation."

According to ABC's Josh Haskell, 24 ambulances lined the street, waiting to be waved in to pick up patients from NYU Langone Medical Center.

"Every 4 minutes a patient comes out and an empty ambulance pulls up. The lobby of the Medical Center is full of hospital personnel, family members, and patients," Haskell reports.

The patients were moved to a number of area hospitals and according to officials at NYU, the receiving hospitals would notify family members.

Sloan Kettering Hospital spokesman Chris Hickey confirmed to ABC News' Gitika Ahuja that it is receiving 26 adult patients from NYU, at their request. Hickey said she didn't know whether they had been admitted yet or what their conditions were.

New York-Presbyterian Hospital spokesman Wade Bryan Dotson said it is also accepting patients from NYU at both campuses, Columbia and Weill Cornell.

Meanwhile, ABC News affiliate WABC captured footage of patients being evacuated; among the first patients brought out of the hospital on gurneys was a mother and her newborn child.

On Monday morning, NYU Langone Medical Center had issued a press release that indicated the hospital's emergency preparedness plan had been activated and that there were "no plans to evacuate" at the time.

Shortly after the reports of an evacuation at NYU Langone, city officials reported that a second major New York City hospital, Bellevue Hospital, was about to lose backup power due to a generator failure.

Requests for more information from NYU Langone Medical Center spokespeople were not immediately returned.